Fuel injectors are operative to spray, via their spray holes, high-pressurized fuel supplied from a common rail, such as a fuel accumulator, in which high-pressurized fuel is charged. These fuel injectors are installed in internal combustion engines and operative to spray high-pressurized fuel into cylinders of the internal combustion engines.
In order to control, with high accuracy, the output torque of internal combustion engines and the characteristics of emissions therefrom, it is required to properly adjust fuel-spray characteristics of fuel injectors, such as the fuel-spray start timing of each fuel injector and the quantity of fuel to be sprayed therefrom.
For meeting such a requirement, there have been proposed techniques that monitor the change in pressure of fuel caused when a fuel injector sprays fuel.
One of the techniques uses a fuel pressure sensor provided directly in the common rail and operative to measure the pressure of fuel charged in the common rail. However, in this technique, the change in pressure of fuel caused when the fuel injector sprays fuel may be somewhat absorbed within the common rail; these results may reduce the accuracy of measuring such a pressure change.
In order to address such a drawback, US Patent Application Publication No. 2008/0228374 corresponding to Japanese Patent Application Publication No. 2008-144749 discloses an alternative one of the techniques that uses a fuel pressure sensor installed in a fuel injector.
Specifically, this technique aims at measuring the change in pressure of fuel caused when the pressure-sensor installed fuel injector sprays fuel without the pressure change being absorbed within the common rail.